I believe that even if a person has a genetic predisposition to gambling, it is not a particular problem because a person can control his actions and refrain from negative experiences.
In my opinion we choose our own destiny and what to do in life. If a gambler blames his losses on his genes, most likely he is afraid to admit his mistakes and tries to blame someone else for his mistakes.
Make sense, but IMO it's not really on the genes. It is when a child witnesses how their parents gambles regularly like it's a normal thing for them that is a part of their daily grind. It will instill in their young minds and will eventually develop into a habit and worse gambling addiction.
So, yeah it is us who chooses our fate on whether or not we engage into gambling excessively.